Vehicle drive device

ABSTRACT

To provide a vehicle drive device capable of efficiently driving a vehicle by using in-wheel motors without falling into the vicious cycle between enhancement of driving via the motors and an increase in vehicle weight. The present invention is a vehicle drive device that uses in-wheel motors to drive a vehicle and includes a vehicle speed sensor that detects the travel speed of a vehicle, in-wheel motors that are provided in wheels of the vehicle and drive the wheels, and a controller that controls the in-wheel motors, in which the controller controls the in-wheel motors so as to generate driving forces when the travel speed of the vehicle detected by the vehicle speed sensor is equal to or more than a predetermined first vehicle speed that is more than zero.

TECHNICAL FIELD

The present invention relates to a vehicle drive device and, moreparticularly, to a vehicle drive device that uses in-wheel motors todrive a vehicle.

BACKGROUND ART

In recent years, exhaust gas regulations for vehicles have been enhancedand demands for fuel efficiency and carbon dioxide emissions per traveldistance for vehicles have become strict in various countries in theworld. In addition, some cities regulate entry of vehicles traveling byan internal combustion engine into urban areas. To satisfy theserequests, hybrid-drive vehicles having an internal combustion engine andmotors and electric vehicles driven only by motors have been developedand widely used.

Japanese Patent No. 5280961 (PTL 1) describes a drive control device forvehicles. In this drive control device, a drive device is provided onthe rear wheel side of the vehicle and two motors provided in this drivedevice drive the rear wheels of the vehicle, respectively. In additionto this drive device, a drive unit formed by connecting an internalcombustion engine and a motor that are in series is provided in thefront portion of the vehicle. The power of the drive unit is transmittedto the front wheels via the transmission and the main drive shaft andthe power of the drive device is transmitted to the rear wheels of thevehicle. In addition, in this drive control device, the two motors ofthe drive device are driven when the vehicle starts, and these drivingforces are transmitted to the rear wheels of the vehicle, respectively.In addition, the driving unit also generates a driving force duringacceleration of the vehicle and the four-wheel drive is achieved by thedriving unit and the two motors of the drive device. As described above,in the drive control device described in PTL 1, the two motors providedmainly for the rear wheels of the vehicle generate the driving forces.

CITATION LIST Patent Literature

PTL 1: Japanese Patent No. 5280961

SUMMARY OF INVENTION Technical Problem

Since the driving of a vehicle by motors does not emit carbon dioxideduring a travel, emission regulations that are enhanced each year can beadvantageously satisfied, but it is difficult to ensure a sufficientlylong distance travel because the electric power that can be stored inthe battery is limited. Accordingly, a hybrid drive device having aninternal combustion engine together with motors is widely used as adrive device for vehicles. In addition, even in such a hybrid drivedevice, in order to reduce carbon dioxide emissions during a travel,vehicles that mainly utilize the driving forces of motors like thevehicle described in PTL 1 are increasing.

Such a hybrid drive device driven mainly by the driving forces of motorsas described above needs to have a large capacity battery to obtainsufficient travel performance. In addition, in order to obtain asufficient driving forces by motors, the motors need to be operated at arelatively high voltage. Accordingly, in a hybrid drive device drivenmainly by the driving forces of motors, since a large capacity batteryis necessary and the electrical system that supplies a high voltage tothe motors needs to be electrically insulated sufficiently, the overallweight of the vehicle increases and the fuel efficiency of the vehiclereduces. Furthermore, in order to drive the vehicle with a heavy weightby the motors, a larger capacity battery and a higher voltage arerequired, thereby causing a vicious cycle that further increases theweight.

In addition, in the drive control device of the vehicle described in PTL1, the motors that drive the rear wheels are directly connected to thedrive shafts of the rear wheels, but the motors may be built into therear wheels to form so-called in-wheel motors. Since the drive shaftsthat couple the motors and the wheels are not required when usingin-wheel motors, it is advantageous in that the weight of the driveshafts can be reduced. However, even when the in-wheel motors areadopted as the motors for startup, acceleration, and cruise travel ofthe vehicle as in the invention described in PTL 1, an increase inweight cannot be avoided because large motors are required to obtainsufficient travel performance. Accordingly, the advantage of usingin-wheel motors cannot be obtained sufficiently.

Accordingly, an object of the present invention is to provide a vehicledrive device capable of efficiently driving a vehicle by using in-wheelmotors without falling into the vicious cycle between enhancement ofdriving by motors and an increase in vehicle weight.

Solution to Problem

To solve the problem described above, according to the presentinvention, there is provided a vehicle drive device that uses anin-wheel motor to drive a vehicle, the vehicle drive device including avehicle speed sensor that detects a travel speed of the vehicle; anin-wheel motor that is provided in a wheel of the vehicle and drives thewheel; and a controller that controls the in-wheel motor, in which thecontroller controls the in-wheel motor so as to generate a driving forcewhen the travel speed of the vehicle detected by the vehicle speedsensor is equal to or more than a predetermined first vehicle speed thatis more than zero.

In the present invention configured as described above, the vehiclespeed sensor detects the travel speed of the vehicle and the controllercontrols the in-wheel motor that is provided in the wheel and drives thewheel. In addition, the controller controls the in-wheel motor so as togenerate a driving force when the travel speed of the vehicle detectedby the vehicle speed sensor is equal to or more than the predeterminedfirst vehicle speed that is more than zero.

In the present invention configured as described above, since thein-wheel motor generate a driving force when the travel speed of thevehicle is equal to or more than the predetermined first vehicle speedthat is more than zero, a large torque from the in-wheel motor is notrequested in the low speed range. As a result, a small motor with asmall torque in the low speed range can be adopted as the in-wheel motorand the vehicle can be efficiently driven using the in-wheel motor.

In the present invention, preferably, the vehicle drive device furtherincludes a body side motor that is provided in a body of the vehicle anddrives the wheel of the vehicle, in which the controller controls thebody side motor so as to generate a driving force when the travel speedof the vehicle detected by the vehicle speed sensor is less than apredetermined second vehicle speed.

In the present invention configured as described above, when the travelspeed of the vehicle is less than the predetermined second vehiclespeed, the body side motor provided in the body of the vehicle generatesthe driving force and can give sufficient travel performance to thevehicle by complementing the in-wheel motor that generates the drivingforce at the first vehicle speed or more.

In the present invention, preferably, the controller also controls thebody side motor so as to generate the driving force when the travelspeed of the vehicle detected by the vehicle speed sensor is equal to ormore than the second vehicle speed.

In the present invention configured as described above, since the bodyside motor also generates the driving force even when the travel speedof the vehicle is equal to or more than the second vehicle speed, boththe body side motor and the in-wheel motor generate the driving forcesin the speed range in which the travel speed is equal to or more thanthe first vehicle speed and the second vehicle speed. Accordingly, thein-wheel motor can be further small-sized.

In the present invention, preferably, the controller controls thein-wheel motor so as not to generate the driving force when the travelspeed of the vehicle detected by the vehicle speed sensor is less thanthe first vehicle speed.

In the present invention configured as described above, since thegeneration of the driving force by the in-wheel motor is prohibited whenthe travel speed of the vehicle is less than the first vehicle speed, asmall motor that generates a very small torque in the low speed rangecan be adopted as the in-wheel motor and the weight of the in-wheelmotor can be reduced.

In the present invention, preferably, the controller starts the vehicleby causing the body side motor to generate the driving force and thencauses the in-wheel motor to generate the driving force when the travelspeed of the vehicle detected by the vehicle speed sensor reaches thefirst vehicle speed.

In the present invention configured as described above, since thein-wheel motor generates the driving force when the travel speed reachesthe first vehicle speed after the body side motor generates the drivingforce and starts the vehicle, a motor with a very small starting torquecan be adopted as the in-wheel motor since the in-wheel motor is notused when the vehicle is started, and the weight of the in-wheel motorcan be reduced.

In the present invention, preferably, the in-wheel motor directly drivesthe wheel in which the in-wheel motor is provided, without interventionof a deceleration mechanism.

In the present invention, since the in-wheel motor generates the drivingforce when the vehicle speed is equal to or more than the predeterminedfirst vehicle speed, the in-wheel motor is not requested for a largetorque in the low speed range. Accordingly, the in-wheel motor cangenerate a sufficient torque without providing the decelerationmechanism in the rotation range in which the in-wheel motor is requestedfor the torque. In addition, in the present invention configured asdescribed above, since the wheel is directly driven without interventionof a deceleration mechanism, the deceleration mechanism with very largeweight can be omitted and an output loss due to the rotation resistanceof the deceleration mechanism can be avoided.

In the present invention, preferably, the in-wheel motor is an inductionmotor.

Generally, an induction motor can obtain a large output torque in thehigh rotation range and the weight thereof can be reduced. Accordingly,by adopting an induction motor as the in-wheel motor that is notrequested for a large torque in the low rotation range in the presentinvention, the weight of a motor capable of generating a sufficienttorque in the required rotation range can be reduced.

In the present invention, preferably, the body side motor is a permanentmagnet motor.

Generally, a permanent magnet motor has a relatively large startingtorque and can obtain a large torque in the low rotation range.Accordingly, by adopting a permanent magnet motor as the body side motorthat is requested for a large torque in the low rotation range in thepresent invention, the weight of a motor capable of generating asufficient torque in the required rotation range can be reduced.

In the present invention, preferably, the wheel driven by the in-wheelmotor is a front wheel of the vehicle and the wheel driven by the bodyside motor is a rear wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor is a rear wheel of the vehicle and the wheel driven by the bodyside motor is a front wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor and the body side motor is a front wheel of the vehicle.

In the present invention, preferably, the wheel driven by the in-wheelmotor and the body side motor is a rear wheel of the vehicle.

In addition, according to the present invention, there is provided avehicle drive device that uses an in-wheel motor to drive a vehicle, thevehicle drive device including a vehicle speed sensor that detects atravel speed of the vehicle; an in-wheel motor that is provided in awheel of the vehicle and drives the wheel; and a controller thatcontrols the in-wheel motor, in which the controller controls thein-wheel motor so as not to generate the driving force when the travelspeed of the vehicle detected by the vehicle speed sensor is less than apredetermined first vehicle speed that is more than zero.

In addition, according to the present invention, there is provided avehicle drive device that uses an in-wheel motor to drive a vehicle, thevehicle drive device including a vehicle speed sensor that detects atravel speed of the vehicle; an in-wheel motor that is provided in awheel of the vehicle and drives the wheel; a body side motor that isprovided in a body of the vehicle and drives the wheel of the vehicle;and a controller that controls the in-wheel motor and the body sidemotor, in which the controller starts the vehicle by causing the bodyside motor to generate the driving force and then causes the in-wheelmotor to generate the driving force when the travel speed of the vehicledetected by the vehicle speed sensor reaches a predetermined firstvehicle speed that is more than zero.

Advantageous Effects of Invention

The vehicle drive device according to the present invention canefficiently drive a vehicle using an in-wheel motor without causing thevicious cycle between enhancement of driving by a motor and an increasein vehicle weight.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first embodiment of the present invention isinstalled.

FIG. 2 is a perspective view, as seen from above, illustrating a frontportion of the vehicle in which the hybrid drive device according to thefirst embodiment of the present invention is installed.

FIG. 3 is a perspective view, as seen from the side, illustrating thefront portion of the vehicle in which the hybrid drive device accordingto the first embodiment of the present invention is installed.

FIG. 4 is a sectional view taken along line iv-iv in FIG. 2.

FIG. 5 is a block diagram illustrating the inputs and outputs of varioussignals in the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 6 is a block diagram illustrating the power supply structure of thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 7 is a diagram schematically illustrating one example of changes involtages when electric power is regenerated into a capacitor in thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 8 is a diagram illustrating the relationship between the outputpower and the vehicle speed of individual motors used in the hybriddrive device according to the first embodiment of the present invention.

FIG. 9 is a sectional view schematically illustrating the structure ofan auxiliary drive motor adopted in the hybrid drive device according tothe first embodiment of the present invention.

FIG. 10 is a flowchart illustrating control by a control device of thehybrid drive device according to the first embodiment of the presentinvention.

FIG. 11 is a graph illustrating examples of operations in individualmodes of the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 12 is a diagram schematically illustrating changes in theacceleration acting on the vehicle when a transmission downshifts orupshifts in the hybrid drive device according to the first embodiment ofthe present invention.

FIG. 13 is a flowchart illustrating control by a control device of ahybrid drive device according to a second embodiment of the presentinvention.

FIG. 14 is a graph illustrating examples of operations in individualmodes of the hybrid drive device according to the second embodiment ofthe present invention.

FIG. 15 is a flowchart illustrating control by a control device of ahybrid drive device according to a third embodiment of the presentinvention.

FIG. 16 is a graph showing examples of operations in individual modes ofthe hybrid drive device according to the third embodiment of the presentinvention.

FIG. 17 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first modification of the present inventionis installed.

FIG. 18 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a second modification of the present inventionis installed.

FIG. 19 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a third modification of the present inventionis installed.

DESCRIPTION OF EMBODIMENTS

Next, preferred embodiments of the present invention will be describedwith reference to the attached drawings.

FIG. 1 is a layout diagram illustrating a vehicle in which a hybriddrive device according to a first embodiment of the present invention isinstalled. FIG. 2 is a perspective view, as seen from the side,illustrating the front portion of a vehicle in which the hybrid drivedevice according to the embodiment is installed and FIG. 3 is aperspective view, as seen from the side, illustrating the front portionof the vehicle. FIG. 4 is a sectional view taken along line iv-iv inFIG. 2.

As illustrated in FIG. 1, a vehicle 1 having the hybrid drive system,which is a vehicle drive device according to the first embodiment of thepresent invention, is a so-called FR (front engine rear drive) vehiclein which an engine 12 as an internal combustion engine is installed inthe front portion (in front of the driver's seat) of the vehicle and apair of left and right rear wheels 2 a as main drive wheels is driven.In addition, as described later, the rear wheels 2 a are also driven bythe main drive motor, which is the main drive electric motor, and a pairof left and right front wheels 2 b, which are auxiliary drive wheels, isdriven by the auxiliary drive motors, which are the auxiliary driveelectric motors.

A hybrid drive device 10 according to the first embodiment of thepresent invention installed in the vehicle 1 includes the engine 12 thatdrives the rear wheels 2 a, a power transmission mechanism 14 thattransmits a driving force to the rear wheels 2 a, a main drive motor 16that drives the rear wheels 2 a, a battery 18 that is an electricstorage unit, auxiliary drive motors 20 that drive the front wheels 2 b,a capacitor 22, and a control device 24 that is a controller.

The engine 12 is an internal combustion engine for generating a drivingforce for the rear wheels 2 a, which are the main drive wheels of thevehicle 1. As illustrated in FIGS. 2 to 4, in the embodiment, an in-line4-cylinder engine is adopted as the engine 12 and the engine 12 disposedin the front portion of the vehicle 1 drives the rear wheels 2 a via thepower transmission mechanism 14. In addition, as illustrated in FIG. 4,in the embodiment, the engine 12 is a flywheel-less engine that does notinclude a flywheel and installed on a subframe 4 a of the vehicle 1 viaengine mounts 6 a. Furthermore, the sub-frame 4 a is fastened and fixedto the lower portions of front side frames 4 b and the lower portion ofa dash panel 4 c at the rear ends thereof.

The power transmission mechanism 14 is configured to transmit thedriving force generated by the engine 12 to the rear wheels 2 a, whichare the main drive wheels. As illustrated in FIG. 1 to FIG. 3, the powertransmission mechanism 14 includes a propeller shaft 14 a connected tothe engine 12, a clutch 14 b, and a transmission 14 c, which is astepped transmission. The propeller shaft 14 a extends from the engine12 disposed in the front portion of the vehicle 1 toward the rear of thevehicle 1 in a propeller shaft tunnel 4 d (FIG. 2). The rear end of thepropeller shaft 14 a is connected to the transmission 14 c via theclutch 14 b. The output shaft of the transmission 14 c is connected tothe axle shaft (not illustrated) of the rear wheels 2 a and drives therear wheels 2 a.

In the embodiment, the transmission 14 c is provided in so-calledtransaxle arrangement. As a result, since the main body of thetransmission with a large outer diameter is not present immediatelybehind the engine 12, the width of the floor tunnel (propeller shafttunnel 4 d) can be reduced, the foot space in the middle of the occupantcan be obtained, and the lower body of the occupant can take asymmetrical posture that faces directly the front. Furthermore, theouter diameter and the length of the main drive motor 16 can easily havesufficient sizes according to the output power thereof while keepingthis posture of the occupant.

The main drive motor 16 is an electric motor for generating a drivingforce for the main drive wheels, provided on the body of the vehicle 1,disposed behind the engine 12 adjacently to the engine 12, and functionsas a body side motor. In addition, an inverter (INV) 16 a is disposedadjacently to the main drive motor 16 and the inverter 16 a converts thecurrent from the battery 18 into alternating current and supplies thealternating current to the main drive motor 16. Furthermore, asillustrated in FIG. 2 and FIG. 3, the main drive motor 16 is connectedin series to the engine 12 and the driving force generated by the maindrive motor 16 is also transmitted to the rear wheels 2 a via the powertransmission mechanism 14. Alternatively, the present invention may beconfigured so that the driving force is transmitted to the rear wheels 2a via a part of the power transmission mechanism 14 by connecting themain drive motor 16 to an intermediate point of the power transmissionmechanism 14. In addition, the embodiment adopts, as the main drivemotor 16, a 25 kW permanent magnet motor (permanent magnet synchronousmotor) driven by 48 V.

The battery 18 is an electric storage unit that stores electric powerfor mainly operating the main drive motor 16. In addition, asillustrated in FIG. 2, the battery 18 is disposed inside the propellershaft tunnel 4 d so as to surround the torque tube 14 d that covers thepropeller shaft 14 a in the embodiment. Furthermore, in the embodiment,a 48 V 3.5 kWh lithium ion battery (LIB) is used as the battery 18.

Since the transaxle arrangement is adopted in the embodiment asdescribed above, the volume for accommodating the battery 18 can beexpanded toward the space in front of the floor tunnel (propeller shafttunnel 4 d) created by this arrangement. This can obtain and expand thecapacity of the battery 18 without reducing the space in the middle ofthe occupant by increasing the width of the floor tunnel.

As illustrated in FIG. 4, the auxiliary drive motors 20 are provided inthe front wheels 2 b under the springs of the vehicle 1 so as togenerate driving forces for the front wheels 2 b, which are theauxiliary drive wheels. In the embodiment, the front wheel 2 b issupported by a double wishbone type suspension and is suspended by anupper arm 8 a, a lower arm 8 b, a spring 8 c, and a shock absorber 8 d.The auxiliary drive motors 20 are in-wheel motors and are housed in thewheels of the front wheels 2 b. Accordingly, the auxiliary drive motors20 are provided in the so-called “under-spring portions” of the vehicle1 so as to drive the front wheels 2 b. In addition, as illustrated inFIG. 1, the current from the capacitor (CAP) 22 is converted intoalternating current by inverters 20 a and supplied to the auxiliarydrive motors 20. Furthermore, in the embodiment, the auxiliary drivemotors 20 are not provided with deceleration machines that aredeceleration mechanisms, the driving forces of the auxiliary drivemotors 20 are directly transmitted to the front wheels 2 b, and thewheels are directly driven. In addition, in the embodiment, 17 kWinduction motors are adopted as the auxiliary drive motors 20.

The capacitor (CAP) 22 is provided so as to store the electric powerregenerated by the auxiliary drive motors 20. As illustrated in FIG. 2and FIG. 3, the capacitor 22 is disposed immediately in front of theengine 12 and supplies electric power to the auxiliary drive motors 20provided in the front wheels 2 b of the vehicle 1. As illustrated inFIG. 4, in the capacitor 22, brackets 22 a projecting from both sidesurfaces thereof are supported by the front side frames 4 b via acapacitor mount 6 b. In addition, a harness 22 b extending from theauxiliary drive motor 20 to the capacitor 22 passes through the upperend of the side wall of the wheel house and is led to the engine room.In addition, the capacitor 22 is configured to store electric charge ata voltage higher than in the battery 18 and is disposed in a regionbetween the left and right front wheels 2 b, which are the auxiliarydrive wheels. The auxiliary drive motors 20, which are driven mainly bythe electric power stored in the capacitor 22, are driven by a voltagehigher than in the main drive motor 16.

The control device 24 controls the engine 12, the main drive motor 16,and the auxiliary drive motors 20 to execute a motor travel mode and aninternal combustion engine travel mode. Specifically, the control device24 can include a microprocessor, a memory, an interface circuit, aprogram for operating these components (these components are notillustrated), and the like. Details on control by the control device 24will be described later.

In addition, as illustrated in FIG. 1, a high voltage DC/DC converter 26a and a low voltage DC/DC converter 26 b, which are voltage convertingunits, are disposed near the capacitor 22. The high voltage DC/DCconverter 26 a, the low voltage DC/DC converter 26 b, the capacitor 22,and the two inverters 20 a are unitized to form an integrated unit.

Next, the overall structure, the power supply structure, and the drivingof the vehicle 1 by the individual motors in the hybrid drive device 10according to the first embodiment of the present invention will bedescribed with reference to FIG. 5 to FIG. 8.

FIG. 5 is a block diagram illustrating the inputs and outputs of varioussignals in the hybrid drive device 10 according to the first embodimentof the present invention. FIG. 6 is a block diagram illustrating thepower supply structure of the hybrid drive device 10 according to thefirst embodiment of the present invention. FIG. 7 is a diagramschematically illustrating one example of changes in voltages whenelectric power is regenerated into the capacitor 22 in the hybrid drivedevice 10 according to the embodiment. FIG. 8 is a diagram illustratingthe relationship between the output power of the motors used in thehybrid drive device 10 according to the embodiment and the vehiclespeed.

First, the inputs and outputs of various signals in the hybrid drivedevice 10 according to the first embodiment of the present inventionwill be described. As illustrated in FIG. 5, the control device 24receives the detection signals detected by a mode selection switch 40, avehicle speed sensor 42, an accelerator position sensor 44, a brakesensor 46, an engine RPM sensor 48, an automatic transmission (AT) inputrotation sensor 50, an automatic transmission (AT) output rotationsensor 52, a voltage sensor 54, and a current sensor 56. In addition,the control device 24 controls the inverter 16 a for the main drivemotor, the inverters 20 a for the auxiliary drive motors 20, the highvoltage DC/DC converter 26 a, the low voltage DC/DC converter 26 b, afuel injection valve 58, a spark plug 60, and a hydraulic solenoid valve62 of the transmission 14 c by control signals to these components.

Next, the power supply structure of the hybrid drive device 10 accordingto the first embodiment of the present invention will be described. Asillustrated in FIG. 6, the battery 18 and capacitor 22 included in thehybrid drive device 10 are connected in series to each other. The maindrive motor 16 is driven by approximately 48 V, which is the referenceoutput voltage of the battery 18, and the auxiliary drive motors 20 aredriven by a maximum voltage of 120 V, which is higher than the sum ofthe output voltage of the battery 18 and the inter-terminal voltage ofthe capacitor 22. Therefore, the auxiliary drive motors 20 are alwaysdriven by the electric power supplied via the capacitor 22.

In addition, the inverter 16 a is mounted to the main drive motor 16 andconverts the output of the battery 18 into alternating current throughwhich the main drive motor 16, which is a permanent magnet motor, isdriven. Similarly, the inverters 20 a are mounted to the auxiliary drivemotors 20 and convert the outputs of the battery 18 and the capacitor 22into alternating current through which the auxiliary drive motors 20,which are induction motors, are driven. Since the auxiliary drive motors20 are driven by a voltage higher than in the main drive motor 16, theharness (electric wires) 22 b that supplies electric power to theauxiliary drive motors 20 needs to have high insulation. However, sincethe capacitor 22 is disposed close to the auxiliary drive motors 20, anincrease in the weight due to high insulation of the harnesses 22 b canbe minimized.

Furthermore, when, for example, the vehicle 1 decelerates, the maindrive motor 16 and the auxiliary drive motors 20 function as generatorsand generate electric power by regenerating the kinetic energy of thevehicle 1. The electric power regenerated by the main drive motor 16 isstored in the battery 18 and the electric power regenerated by theauxiliary drive motors 20 is stored mainly in the capacitor 22.

In addition, the high voltage DC/DC converter 26 a, which is a voltageconverting unit, is connected between the battery 18 and the capacitor22 and this high voltage DC/DC converter 26 a charges the capacitor 22by raising the voltage of the battery 18 when the electric charge storedin the capacitor 22 is insufficient (when the inter-terminal voltage ofthe capacitor 22 drops). In contrast, when the inter-terminal voltage ofthe capacitor 22 rises to a predetermined voltage or higher due toregeneration of energy by the auxiliary drive motors 20, the battery 18is charged by reducing the electric charge stored in the capacitor 22and applying the electric charge to the battery 18. That is, theelectric power regenerated by the auxiliary drive motors 20 is stored inthe capacitor 22, and then the battery 18 is charged with a part of thestored electric charge via the high voltage DC/DC converter 26 a.

Furthermore, the low voltage DC/DC converter 26 b is connected betweenthe battery 18 and 12V electric components 25 of the vehicle 1. Sincemany of the control device 24 of the hybrid drive device 10 and theelectric components 25 of the vehicle 1 operate at a voltage of 12V, thevoltage of the electric charge stored in the battery 18 is reduced to12V by the low voltage DC/DC converter 26 b and supplied to thesedevices.

Next, charging and discharging of the capacitor 22 will be describedwith reference to FIG. 7.

As illustrated in FIG. 7, the voltage of the capacitor 22 is the sum ofthe base voltage of the battery 18 and the inter-terminal voltage of thecapacitor 22 itself. When, for example, the vehicle 1 decelerates, theauxiliary drive motors 20 regenerate electric power and the capacitor 22is charged with the regenerated electric power. When the capacitor 22 ischarged, the inter-terminal voltage rises relatively rapidly. When theinter-terminal voltage of the capacitor 22 rises to a predeterminedvoltage or more due to the charging, the voltage of the capacitor 22 isreduced by the high voltage DC/DC converter 26 a and the battery 18 ischarged. As illustrated in FIG. 7, the charging to the battery 18 fromthe capacitor 22 is performed relatively slowly than the charging to thecapacitor 22 and the voltage of the capacitor 22 drops to a propervoltage relatively slowly.

That is, the electric power regenerated by the auxiliary drive motors 20is temporarily stored in the capacitor 22 and then the battery 18 isslowly charged with the regenerated electric power. Depending on thetime when the regeneration is performed, the regeneration of electricpower by the auxiliary drive motors 20 may overlap with the chargingfrom the capacitor 22 to the battery 18.

In contrast, the battery 18 is directly charged with the electric powerregenerated by the main drive motor 16.

Next, the relationship between the vehicle speed and the output power ofthe motors in the hybrid drive device 10 according to the firstembodiment of the present invention will be described with reference toFIG. 8. FIG. 8 is a graph illustrating the relationship between thespeed of the vehicle 1 and the output power of the motors in the hybriddrive device 10 according to the embodiment. In FIG. 8, the output powerof the main drive motor 16 is represented by a dotted line, the outputpower of one of the auxiliary drive motors 20 is represented by adot-dash line, the sum of the output power of the two auxiliary drivemotors 20 is represented by a dot-dot-dash line, and the sum of theoutput power of all motors is represented by a solid line. Although FIG.8 illustrates the speed of the vehicle 1 on the horizontal axis and theoutput power of the motors on the vertical axis, since there is acertain relationship between the speed of the vehicle 1 and the numberof revolutions of each of the motors, the output power of the motorsdraws curves similar to those in FIG. 8 even when the number ofrevolutions of each of the motors is represented on the horizontal axis.

Since a permanent magnet motor is adopted as the main drive motor 16 inthe embodiment, as represented by the dotted line in FIG. 8, the outputpower of the main drive motor 16 is large in a low vehicle speed rangein which the number of revolutions of the motor is low and the motoroutput power that can be output reduces as the vehicle speed increases.That is, in the embodiment, the main drive motor 16 is driven byapproximately 48 V, outputs a torque (maximum torque) of approximately200 Nm up to approximately 1000 rpm, and the torque reduces with theincrease in the number of revolutions at approximately 1000 rpm or more.In addition, in the embodiment, the main drive motor 16 is configured toobtain a continuous output power of approximately 20 kW and a maximumoutput power of approximately 25 kW in the lowest low speed range.

In contrast, since induction motors are used as the auxiliary drivemotors 20, the output power of the auxiliary drive motors 20 is verysmall in the low vehicle speed range, the output power increases as thespeed becomes higher, the maximum output power is obtained at a vehiclespeed close to 130 km/h or so, and then the motor output power reduces,as represented by the dot-dash line and the dot-dot-dash line in FIG. 8.In the embodiment, the auxiliary drive motors 20 are driven byapproximately 120 V, and each of them obtains an output power ofapproximately 17 kW and the two motors obtain a total output power ofapproximately 34 kW at a vehicle speed close to 130 km/h or so. That is,in the embodiment, each of the auxiliary drive motors 20 has a peak ofthe torque curve and obtains a maximum torque of approximately 200 Nm atapproximately 600 to 800 rpm.

The solid line in FIG. 8 represents the sum of the output power of themain drive motor 16 and the two auxiliary drive motors 20. As is clearfrom this graph, in the embodiment, a maximum output power ofapproximately 53 kW is obtained at a vehicle speed close to 130 km/h orso and the travel condition requested in the WLTP test at this vehiclespeed is satisfied at this maximum output power. In addition, althoughthe output power values of the two auxiliary drive motors 20 are summedup even in the low vehicle speed range as represented by the solid linein FIG. 8, the auxiliary drive motors 20 are actually not driven in thelow vehicle speed range as described later. That is, the vehicle isdriven only by the main drive motor 16 at startup and in a low vehiclespeed range and the two auxiliary drive motors 20 generate output poweronly when large output power is required in the high vehicle speed range(for example, when the vehicle 1 is accelerated in the high vehiclespeed range). By using the induction motors (auxiliary drive motors 20)capable of generating large output power in the high rotation range onlyin the high speed range as described above, sufficient output power canbe obtained when necessary (for example, when acceleration at apredetermined speed or more is performed) while an increase in vehicleweight is kept low.

Next, the structure of the auxiliary drive motors 20 adopted in thehybrid drive device 10 according to the first embodiment of the presentinvention will be described with reference to FIG. 9. FIG. 9 is asectional view schematically illustrating the structure of the auxiliarydrive motor 20.

As illustrated in FIG. 9, the auxiliary drive motor 20 is an outer rotortype induction motor including a stator 28 and a rotor 30 that rotatesaround this stator.

The stator 28 includes a substantially discoid stator base 28 a, astator shaft 28 b extending from the center of the stator base 28 a, anda stator coil 28 c attached around the stator shaft 28 b. In addition,the stator coil 28 c is housed in an electrical insulating liquidchamber 32, immersed in electrical insulating liquid 32 a that fills theelectrical insulating liquid chamber, and subject to boiling cooling viathe liquid.

The rotor 30 is formed in a substantially cylindrical shape so as tosurround the periphery of the stator 28 and has a substantiallycylindrical rotor body 30 a with one end closed and a rotor coil 30 bdisposed on the inner peripheral wall surface of the rotor body 30 a.The rotor coil 30 b is disposed facing the stator coil 28 c so as togenerate induction current by the rotational magnetic field generated bythe stator coil 28 c. In addition, the rotor 30 is supported by abearing 34 attached to the end of the stator shaft 28 b so as to rotatesmoothly around the stator 28.

The stator base 28 a is supported by an upper arm 8 a and a lower arm 8b (FIG. 4) that suspend the front wheels of the vehicle 1. In contrast,the rotor body 30 a is directly fixed to the wheels of the front wheels2 b (not illustrated). Alternating current converted by the inverters 20a flows through the stator coil 28 c and generates a rotational magneticfield. This rotational magnetic field causes an induced current to flowthrough the rotor coil 30 b and generates a driving force that rotatesthe rotor body 30 a. As described above, the driving forces generated bythe auxiliary drive motors 20 rotationally drives the wheels of thefront wheels 2 b (not illustrated) directly.

Next, the operation of the motor travel mode and the operation of theinternal combustion engine travel mode performed by the control device24 will be described with reference to FIG. 10 and FIG. 11. FIG. 10 is aflowchart illustrating control by the control device 24 and FIG. 11 is agraph illustrating examples of the operations of these modes. Theflowchart illustrated in FIG. 10 is repeatedly executed at predeterminedtime intervals while the vehicle 1 operates.

The graph illustrated in FIG. 11 represents, in order from the top, thespeed of the vehicle 1, the torque generated by the engine 12, thetorque generated by the main drive motor 16, the torque generated by theauxiliary drive motors 20, the voltage of the capacitor 22, the currentof the capacitor 22, and the current of the battery 18. In the graphrepresenting the torque of the main drive motor 16 and the torques ofthe auxiliary drive motors 20, positive values mean the state in whichmotors generate torques and negative values mean the state in whichmotors regenerate the kinetic energy of the vehicle 1. In addition, inthe graph representing the current of the capacitor 22 and the currentof the battery 18, negative values mean the state in which electricpower is supplied (discharged) to motors and positive values mean thestate of charging with the electric power regenerated by motors.

First, in step S1 in FIG. 10, it is determined whether the vehicle 1 hasbeen set to the internal combustion engine travel mode (ENG mode). Thatis, the vehicle 1 has the mode selection switch 40 (FIG. 5) that selectseither the internal combustion engine travel mode or the motor travelmode (EV mode) and it is determined in step S1 which mode has been set.Since the motor travel mode is set at time ti in FIG. 11, the processingof the flowchart in FIG. 10 proceeds to step S2.

Next, in step S2, it is determined whether the speed of the vehicle 1 isequal to or more than a predetermined vehicle speed. The processingproceeds to step S6 when the speed is equal to or more than thepredetermined vehicle speed or the processing proceeds to step S3 whenthe speed is less than the predetermined vehicle speed. Since the driverhas started the vehicle 1 and the vehicle speed is low at time t₁ inFIG. 11, the processing of the flowchart proceeds to step S3.

Furthermore, in step S3, it is determined whether the vehicle 1 isdecelerating (whether the brake pedal (not illustrated) of the vehicle 1is being operated). The processing proceeds to step S5 when the vehicle1 is decelerating or the processing proceeds to step S4 when the vehicle1 is accelerating or traveling at a constant speed (when the brakesensor 46 (FIG. 5) does not detect the operation of the brake pedal).Since the driver has started the vehicle 1 and is accelerating thevehicle 1 (accelerator position sensor 44 (FIG. 5) has detected that theaccelerator pedal of the vehicle 1 has been operated by a predeterminedamount or more) at time t₁ in FIG. 11, the processing of the flowchartproceeds to step S4 and the processing of the flowchart in FIG. 10 iscompleted once. In step S4, the main drive motor 16 generates a torqueand the vehicle speed increases (from time t₁ to time t₂ in FIG. 11). Atthis time, since discharge current flows from the battery 18 thatsupplies electric power to the main drive motor 16 and discharge currentfrom the capacitor 22 remains zero because the auxiliary drive motors 20do not generate torques, the voltage of the capacitor 22 does notchange. The current and voltage are detected by the voltage sensor 54and the current sensor 56 (FIG. 5) and input to the control device 24.In addition, from time t₁ to time t₂ in FIG. 11, the engine 12 is notdriven because the motor travel mode is set. That is, since the controldevice 24 stops fuel injection via the fuel injection valve 58 of theengine 12 and does not perform ignition via the ignition plug 60, theengine 12 does not generate a torque.

In the example illustrated in FIG. 11, the vehicle 1 accelerates fromtime t₁ to time t₂ and then travels at a constant speed until time t₃.In this period, the processing of steps S1, S2, S3, and S4 in theflowchart in FIG. 10 is repeatedly executed. During this low speedtravel, since the torque generated by the main drive motor 16 becomessmaller than the torque during the acceleration, the current dischargedfrom the battery 18 also becomes smaller.

Next, when the driver operates the brake pedal (not illustrated) of thevehicle 1 at time t₃ in FIG. 11, the processing of the flowchart in FIG.10 proceeds to step S5 from step S3. In step S5, the driving by the maindrive motor 16 is stopped (no torque is generated) and the kineticenergy of the vehicle 1 is regenerated as electric power by theauxiliary drive motors 20. The vehicle 1 is decelerated by theregeneration of the kinetic energy, the discharge current from battery18 becomes zero, the charge current flows through the capacitor 22because the electric power is regenerated by the auxiliary drive motors20, and the voltage of the capacitor 22 rises.

When the vehicle 1 stops at time t₄ in FIG. 11, the charge current tothe capacitor 22 becomes zero and the voltage of the capacitor 22 alsobecomes constant. Next, the vehicle 1 is started again at time t₅ andreaches a constant speed travel (time t6), and the processing of stepsS1, S2, S3, and S4 in the flowchart in FIG. 10 is repeatedly executeduntil the deceleration of the vehicle 1 is started (time t₇). When thedeceleration of the vehicle is started at time t₇, the processing ofsteps s1, S2, S3, and S5 in the flowchart in FIG. 10 is repeatedlyexecuted and the auxiliary drive motors 20 regenerates electric power.As described above, the motor travel mode is set while the vehiclestarts and stops repeatedly at a relatively low speed in urban areas orthe like, the vehicle 1 functions purely as an electric vehicle (EV) andthe engine 12 does not generate a torque.

Furthermore, when the vehicle 1 is started at time t₈ in FIG. 11, theprocessing of steps S1, S2, S3, and S4 in the flowchart in FIG. 10 isrepeatedly executed and the vehicle 1 is accelerated. Next, when thespeed of the vehicle 1 detected by the vehicle speed sensor 42 (FIG. 5)exceeds a predetermined first vehicle speed at time t₉, the processingof the flowchart proceeds to step S6 from step S2. In step S6, it isdetermined whether the vehicle 1 is decelerating (the brake pedal isbeing operated). Since the vehicle 1 is not decelerating at time t9, theprocessing of the flowchart proceeds to step S7. In step S7, it isdetermined whether the vehicle 1 is accelerating by a predeterminedvalue or more (whether the accelerator pedal of the vehicle 1 has beenoperated by a predetermined amount or more). In the embodiment, thepredetermined first vehicle speed is set to approximately 100 km/h,which is more than a travel speed of 0 km/h.

Since the vehicle 1 is accelerating by a predetermined value or more attime t₉ in the example illustrated in FIG. 11, the processing proceedsto step S8, in which the main drive motor 16 is driven and the auxiliarydrive motors 20 are also driven. When the vehicle 1 is accelerated by apredetermined value or more at the predetermined first vehicle speed ormore in the motor travel mode as described above, electric power issupplied to the main drive motor 16 and the auxiliary drive motors 20 toobtain the required power, and this drives the vehicle 1. In otherwords, the control device 24 starts the vehicle 1 (time t₈) by causingthe main drive motor 16 to generate a driving force and then causes theauxiliary drive motors 20 to generate driving forces when the travelspeed of the vehicle 1 detected by the vehicle speed sensor 42 reachesthe first vehicle speed (time t₉). At this time, the battery 18 supplieselectric power to the main drive motor 16 and the capacitor 22 supplieselectric power to the auxiliary drive motors 20. Since the capacitor 22supplies electric power as described above, the voltage of the capacitor22 drops. While the vehicle 1 is driven by the main drive motor 16 andthe auxiliary drive motors 20 (from time t₉ to time t₁₀), the processingof steps S1, S2, S6, S7, and S8 in the flowchart is repeatedly executed.

As described above, the auxiliary drive motors 20 generate drivingforces when the travel speed of the vehicle 1 is equal to or more thanthe predetermined first vehicle speed and are prohibited from generatingdriving forces when the travel speed is less than the first vehiclespeed. Although the first vehicle speed is set to approximately 100 km/hin the embodiment, the first vehicle speed may be set to any vehiclespeed that is equal to or more than approximately 50 km/h according tothe output characteristics of the adopted auxiliary drive motors 20. Incontrast, the main drive motor 16 generates a driving force when thetravel speed of the vehicle 1 is less than a predetermined secondvehicle speed including zero or when the travel speed is equal to ormore than the second vehicle speed. The predetermined second vehiclespeed may be set to a vehicle speed identical to or different from thefirst vehicle speed. In addition, in the embodiment, the main drivemotor 16 always generates a driving force when the driving force isrequested in the motor travel mode.

Next, when the vehicle 1 shifts to a constant speed travel (when theaccelerator pedal is operated by less than a predetermined amount) attime t₁₀ in FIG. 11, the processing of steps S1, S2, S6, S7, and S9 inthe flowchart is repeatedly executed. In step S9, driving by theauxiliary drive motors 20 is stopped (no torque is generated) and thevehicle 1 is driven only by the main drive motor 16. Even when thevehicle 1 travels at the predetermined vehicle speed or more, thevehicle 1 is driven only by the main drive motor 16 if the accelerationis less than the predetermined amount.

In addition, since the voltage of the capacitor 22 drops to thepredetermined value or less because the capacitor 22 has driven theauxiliary drive motors 20 from time t₉ to time t₁₀, the control device24 sends a signal to the high voltage DC/DC converter 26 a at time t₁₀to charge the capacitor 22. That is, the high voltage DC/DC converter 26a raises the voltage of the electric charge stored in the battery 18 andcharges the capacitor 22. This causes the current for driving the maindrive motor 16 and the current for charging the capacitor 22 to bedischarged from the battery 18 from time t₁₀ to time t₁₁ in FIG. 11. Iflarge electric power is regenerated by the auxiliary drive motors 20 andthe voltage of the capacitor 22 rises to a predetermined value or more,the control device 24 sends a signal to the high voltage DC/DC converter26 a to reduce the voltage of the capacitor 22 and charges the battery18. As described above, the electric power regenerated by the auxiliarydrive motors 20 is consumed by the auxiliary drive motors 20, or storedin the capacitor 22 and then used to charge the battery 18 via the highvoltage DC/DC converter 26 a.

When the vehicle 1 decelerates (the brake pedal is operated) at time t₁₁in FIG. 11, the processing of steps S1, S2, S6, and S10 in the flowchartwill be repeatedly executed. In step S10, the kinetic energy of thevehicle 1 is regenerated as electric power by both the main drive motor16 and the auxiliary drive motors 20. The electric power regenerated bythe main drive motor 16 is stored in the battery 18 and the electricpower regenerated by the auxiliary drive motors 20 is stored in thecapacitor 22. As described above, when the brake pedal is operated atthe specified vehicle speed or more, electric power is regenerated byboth the main drive motor 16 and the auxiliary drive motors 20 andelectric charge is stored in the capacitor 22 and the battery 18.

Next, at time t₁₂ in FIG. 11, the driver switches the mode of thevehicle 1 from the motor travel mode to the internal combustion enginetravel mode by operating the mode selection switch 40 (FIG. 5) anddepresses the accelerator pedal (not illustrated). When the mode of thevehicle 1 is switched to the internal combustion engine travel mode, theprocessing of the flowchart in FIG. 10 by the control device 24 proceedsto step S11 from step S1, and the processing of step S11 and subsequentsteps is executed.

First, in step S11, it is determined whether the vehicle 1 stops. Whenthe vehicle 1 does not stop (the vehicle 1 is traveling), it isdetermined in step S12 whether the vehicle 1 is decelerating (whetherthe brake pedal (not illustrated) is being operated). Since the vehicle1 is traveling and the driver is operating the accelerator pedal at timet₁₂ in FIG. 11, the processing of the flowchart in FIG. 10 proceeds tostep S13.

In step S13, the supply of fuel to the engine 12 starts and the engine12 generates a torque. That is, since the output shaft (not illustrated)of the engine 12 is directly connected to the output shaft (notillustrated) of the main drive motor 16 in the embodiment, the outputshaft of the engine 12 always rotates together with driving by the maindrive motor 16. However, the engine 12 does not generate a torque in themotor travel mode because fuel supply to the engine 12 is performed,but, in the internal combustion engine travel mode, the engine 12generates a torque because fuel supply (fuel injection by the fuelinjection valve 58 and ignition by the ignition plug 60) starts.

In addition, immediately after switching from the motor travel mode tothe internal combustion engine travel mode, the control device 24 causesthe main drive motor 16 to generate a torque for starting the engine(from time t₁₂ to time t₁₃ in FIG. 11). This torque for starting theengine is generated to cause the vehicle 1 to travel until the engine 12actually generates a torque after fuel supply to the engine 12 isstarted and suppress torque fluctuations before and after the engine 12generates a torque. In addition, in the embodiment, when the number ofrevolutions of the engine 12 at the time of switching to the internalcombustion engine travel mode is less than a predetermined number ofrevolutions, fuel supply to the engine 12 is not started and the fuelsupply is started when the number of revolutions of the engine 12 isequal to or more than the predetermined number of revolutions due to thetorque for starting the engine. In the embodiment, when the number ofrevolutions of the engine 12 detected by the engine RPM sensor 48 risesto 2000 rpm or more, fuel supply is started.

While the vehicle 1 accelerates or travels at a constant speed after theengine 12 is started, the processing of steps S1, S11, S12, and S13 inthe flowchart in FIG. 10 is repeatedly executed (from time t₁₃ to timet₁₄ in FIG. 11). As described above, in the internal combustion enginetravel mode, the engine 12 exclusively outputs the power for driving thevehicle 1 and the main drive motor 16 and the auxiliary drive motors 20do not output the power for driving the vehicle 1. Accordingly, thedriver can enjoy the driving feeling of the vehicle 1 driven by theinternal combustion engine.

Next, when the driver operates the brake pedal (not illustrated) at timet₁₄ in FIG. 11, the processing of the flowchart in FIG. 10 proceeds tostep S14 from step S12. In step S14, fuel supply to the engine 12 isstopped and fuel consumption is suppressed. Furthermore, in step S15,the main drive motor 16 and the auxiliary drive motors 20 regenerate thekinetic energy of the vehicle 1 as electric energy and charge currentflows through the battery 18 and the capacitor 22. As described above,during deceleration of the vehicle 1, the processing of steps S1, S11,S12, S14, and S15 is repeatedly executed (from time t₁₄ to time t₁₅ inFIG. 11).

During deceleration of the vehicle 1 in the internal combustion enginetravel mode, the control device 24 performs downshift torque adjustmentby driving the auxiliary drive motors 20 in switching (shifting) of thetransmission 14 c, which is a stepped transmission. The torque generatedby this torque adjustment complements an instantaneous torque drop orthe like and is not equivalent to the torque that drives the vehicle 1.Details on torque adjustment will be described later.

On the other hand, when the vehicle 1 stops at time t₁₅ in FIG. 11, theprocessing of the flowchart in FIG. 10 proceeds to step S16 from stepS11. In step S16, the control device 24 supplies the minimum fuelrequired to maintain the idling of the engine 12. In addition, thecontrol device 24 generates an assist torque via the main drive motor 16so that the engine 12 can maintain idling at a low number ofrevolutions. As described above, while the vehicle 1 stops, theprocessing of steps S1, S11, and S16 is repeatedly executed (from timet₁₅ to time t₁₆ in FIG. 11).

Although the engine 12 is a flywheel-less engine in the embodiment,since the assist torque generated by the main drive motor 16 acts as apseudo flywheel, the engine 12 can maintain smooth idling at a lownumber of revolutions. In addition, adoption of a flywheel-less enginemakes the response of the engine 12 high during a travel in the internalcombustion engine travel mode, thereby enabling driving with a goodfeeling.

In addition, when the vehicle 1 starts from a stop state in the internalcombustion engine travel mode, the control device 24 increases thenumber of revolutions of the main drive motor 16 (the number ofrevolutions of the engine 12) to a predetermined number of revolutionsby sending a signal to the main drive motor 16. After the number ofrevolutions of the engine is increased to the predetermined number ofrevolutions, the control device 24 supplies the engine 12 with fuel fordriving the engine, causes the engine 12 to perform driving, andperforms a travel in the internal combustion engine travel mode.

Next, torque adjustment during switching (shifting) of the transmission14 c will be described with reference to FIG. 12.

FIG. 12 is a diagram that schematically illustrates changes in theacceleration that acts on the vehicle when transmission 14 c downshiftsor upshifts, and represents, in order from the top, examples ofdownshift torque down, downshift torque assistance, and upshift torqueassistance.

In the internal combustion engine travel mode, the hybrid drive device10 according to the first embodiment of the present invention causes thecontrol device 24 to automatically switch the clutch 14 b and thetransmission 14 c, which is an automatic transmission, according to thevehicle speed and the number of revolutions of the engine when theautomatic shift mode is set. As illustrated in the upper part of FIG.12, when the transmission 14 c downshifts (shifts to a low speed) withnegative acceleration acting on the vehicle 1 during deceleration (timet₁₀₁ in FIG. 12), the control device 24 disconnects the clutch 14 b todisconnect the output shaft of the engine 12 from the main drive wheels(rear wheels 2 a). When the engine 12 is disconnected from the maindrive wheels in this way, since the rotation resistance of the engine 12no longer acts on the main drive wheels, the acceleration acting on thevehicle 1 instantaneously changes to a positive side, as indicated bythe dotted line in the upper part of FIG. 12. Next, the control device24 sends a control signal to the transmission 14 c and switches thebuilt-in hydraulic solenoid valve 62 (FIG. 5) to increase the reductionratio of the transmission 14 c. Furthermore, when the control device 24connects the clutch 14 b at time t₁₀₂ at which the downshift iscompleted, the acceleration changes to a negative side again. Althoughthe period from the start to the completion of a downshift (from timet₁₀₁ to time t₁₀₂) is generally 300 to 1000 msec, the occupant is givenan idle running feeling and may have a discomfort feeling due to aso-called torque shock in which the torque acting on the vehicleinstantaneously changes.

In the hybrid drive device 10 according to the embodiment, the controldevice 24 makes torque adjustment by sending a control signal to theauxiliary drive motors 20 at the time of a downshift to suppress theidle running feeling of the vehicle 1. Specifically, when the controldevice 24 performs a downshift by sending a signal to the clutch 14 band the transmission 14 c, the control device 24 reads the number ofrevolutions of the input shaft and the number of revolutions of theoutput shaft of the transmission 14 c detected by the automatictransmission input rotation sensor 50 and the automatic transmissionoutput rotation sensor 52 (FIG. 5), respectively. Furthermore, thecontrol device 24 predicts changes in the acceleration generated in thevehicle 1 based on the number of revolutions of the input shaft and thenumber of revolutions of the output shaft that have been read and causesthe auxiliary drive motors 20 to regenerate energy. This suppresses aninstantaneous rise in the acceleration (change to the positive side) ofthe vehicle 1 due to a torque shock as indicated by the solid line inthe upper part of FIG. 12, thereby suppressing an idling runningfeeling. Furthermore, in the embodiment, the torque shock in the maindrive wheels (rear wheels 2 a) caused by a downshift is complemented bythe auxiliary drive wheels (front wheels 2 b) via the auxiliary drivemotors 20. Accordingly, torque adjustment can be made without beingaffected by the dynamic characteristics of the power transmissionmechanism 14 that transmits power from the engine 12 to the main drivewheels.

In addition, as indicated by the dotted line in the middle part of FIG.12, when a downshift is started at time t₁₀₃ with positive accelerationacting on the vehicle 1 during acceleration, the output shaft of theengine 12 is disconnected from the main drive wheels (rear wheels 2 a).Accordingly, since the drive torque by the engine 12 does not act on therear wheels 2 a and a torque shock occurs, the occupant may be given astall feeling by the time the downshift is completed at time t₁₀₄. Thatis, the acceleration of the vehicle 1 instantaneously changes to thenegative side at time t₁₀₃ at which a downshift is started and theacceleration changes to the positive side at time t₁₀₄ at which thedownshift is completed.

In the hybrid drive device 10 according to the embodiment, whenperforming a downshift, the control device 24 predicts changes in theacceleration caused in the vehicle 1 based on detection signals from theautomatic transmission input rotation sensor 50 and the automatictransmission output rotation sensor 52 and causes the auxiliary drivemotors 20 to generate driving forces. As indicated by the solid line inthe middle part of FIG. 12, this suppresses an instantaneous drop(change to the negative side) of the acceleration of the vehicle 1 by atorque shock and suppresses a stall feeling.

Furthermore, as indicated by the dotted line in the lower part of FIG.12, when an upshift is started at time t₁₀₅ with positive accelerationacting on the vehicle 1 (positive acceleration reduces with time) duringacceleration, the output shaft of the engine 12 is disconnected from themain drive wheels (rear wheels 2 a). Accordingly, since the drive torqueby the engine 12 does not act on the rear wheels 2 a and a torque shockoccurs, the occupant may be given a stall feeling by the time theupshift is completed at time t₁₀₆. That is, the acceleration of thevehicle 1 instantaneously changes to the negative side at time t₁₀₅ atwhich the upshift is started and the acceleration changes to thepositive side at time t₁₀₆ at which the upshift is completed.

In the embodiment, when performing an upshift, the control device 24predicts changes in the acceleration caused in the vehicle 1 based ondetection signals from the automatic transmission input rotation sensor50 and the automatic transmission output rotation sensor 52 and causesthe auxiliary drive motors 20 to generate driving forces. As indicatedby the solid line in the lower part of FIG. 12, this suppresses aninstantaneous drop (change to the negative side) of the acceleration ofthe vehicle 1 due to a torque shock and suppresses a stall feeling.

As described above, the adjustment of the drive torque by the auxiliarydrive motors 20 during a downshift or an upshift of the transmission 14c is performed in a very short time and does not substantially drive thevehicle 1. Therefore, the power generated by the auxiliary drive motors20 can be generated by the electric charge regenerated by the auxiliarydrive motors 20 and stored in the capacitor 22. In addition, theadjustment of the drive torque by the auxiliary drive motors 20 can beapplied to an automatic transmission with a torque converter, anautomatic transmission without a torque converter, an automated manualtransmission, and the like.

In the hybrid drive device 10 according to the first embodiment of thepresent invention, since the auxiliary drive motors 20, which arein-wheel motors, generate driving forces when the travel speed of thevehicle 1 is equal to or more than the predetermined first vehicle speedthat is more than zero (from step S2 to step S6 in FIG. 10), theauxiliary drive motors 20 are not requested to generate a large torquein the low speed range. As a result, small motors with a low torque inthe low speed range can be adopted as the auxiliary drive motors 20 andthe vehicle can be efficiently driven by using the in-wheel motors.

In addition, in the hybrid drive device 10 according to the embodiment,since the main drive motor 16, which is the body side motor provided inthe body of the vehicle 1, generates a driving force (step S4 in FIG.10) when the travel speed of the vehicle 1 is less than thepredetermined second vehicle speed (from step S2 to step S3 in the FIG.10), the main drive motor 16 can complement the auxiliary drive motors20, which are in-wheel motors generating driving forces when the vehiclespeed is the first vehicle speed or more, and can provide sufficienttravel performance for the vehicle 1.

Furthermore, in the hybrid drive device 10 according to the embodiment,since the main drive motor 16 generates a driving force (steps S8 andstep S9 in FIG. 10) even when the travel speed of the vehicle 1 is equalto or more than the second vehicle speed (from step S2 to step S6 inFIG. 10), both the main drive motor 16 and the auxiliary drive motors 20generate driving forces in the speed range in which the travel speed isequal to or more than the first and second vehicle speeds. Accordingly,the in-wheel motors, which are the auxiliary drive motors 20, can befurther small-sized.

In addition, in the hybrid drive device 10 according to the embodiment,since the auxiliary drive motors 20 are prohibited from generatingdriving forces (step S4 and step S5 in FIG. 10) when the travel speed ofthe vehicle 1 is less than the first vehicle speed (from step S2 to stepS3 in FIG. 10), motors with a very small torque in the low speed rangecan be adopted as the auxiliary drive motors 20 and the weight of thein-wheel motors can be reduced.

Furthermore, in the hybrid drive device 10 according to the embodiment,the auxiliary drive motors 20, which are in-wheel motors, generatedriving forces when the travel speed reaches the first vehicle speed(time t₉ in FIG. 11) after the main drive motor 16, which is a body sidemotor, generates a driving force and starts the vehicle 1 (time t₈ inFIG. 11), so the in-wheel motors are not used to start the vehicle 1,motors with a very small starting torque can be adopted as the in-wheelmotors, and the weight of the in-wheel motors can be reduced.

In addition, in the hybrid drive device 10 according to the embodiment,since the wheels (front wheels 2 b) are directly driven by the auxiliarydrive motors 20 without intervention of a deceleration mechanism (FIG. 4and FIG. 9), the deceleration mechanism with very heavy weight can beomitted and the output loss due to the rotation resistance of thedeceleration mechanism can be avoided.

Furthermore, in the hybrid drive device 10 according to the embodiment,by adopting induction motors as the in-wheel motors that are theauxiliary drive motors 20 (step S8 in FIG. 10) not requested for a largetorque in the low rotation range (FIG. 4 and FIG. 9), lightweight motorscapable of generating a sufficient torque in the required rotation rangecan be achieved.

In addition, in the hybrid drive device 10 according to the embodiment,by adopting a permanent magnet motor as the main drive motor 16requested for a large torque in the low rotation range (step S4 in FIG.10), a lightweight motor capable of generating a sufficient torque inthe required rotation range can be achieved.

Next, a vehicle drive device that is a hybrid drive device according toa second embodiment of the present invention will be described withreference to FIG. 13 and FIG. 14.

The vehicle drive device according to the embodiment is different fromthat of the first embodiment in the control executed by the controldevice 24. Accordingly, since the structure of the vehicle drive devicedescribed with reference to FIG. 1 to FIG. 9 is the same as that of thefirst embodiment, the description thereof will be omitted and only thepoints of the second embodiment of the present invention that aredifferent from those of the first embodiment will be described here.

FIG. 13 is a flowchart illustrating control by the control deviceinstalled in the vehicle drive device according to the second embodimentof the present invention and FIG. 14 is a graph illustrating one exampleof operation in the motor travel mode. The flowchart illustrated in FIG.13 indicates the processing (corresponding to the processing of step S2and subsequent steps in the flowchart illustrated in FIG. 10) executedwhen the mode selection switch 40 of the vehicle 1 is set to the motortravel mode. The processing executed in the engine travel mode of thevehicle control device according to the embodiment is the same as thatof the first embodiment. In addition, the flowchart illustrated in FIG.13 is repeatedly executed at predetermined time intervals while thevehicle 1 operates.

The graph illustrated in FIG. 14 represents, in order from the top, thespeed of the vehicle 1, the target acceleration of the vehicle 1 that isset based on a driving operation by the driver, the torque generated bythe engine 12, the torque generated by the main drive motor 16, and thetorque generated by the auxiliary drive motors 20. Since the graphillustrated in FIG. 14 represents the operation in the motor travelmode, the torque generated by the engine 12 is always set to zero. Inaddition, in the graph representing the torque of the main drive motor16 and the torque of the auxiliary drive motors 20, positive values meanthat motors are generating torques and negative values mean that motorsare regenerating the kinetic energy of the vehicle 1.

First, in step S201 in FIG. 13, detection signals from various sensorsare read. Specifically, detection signals from the vehicle speed sensor42, the accelerator position sensor 44, the brake sensor 46, and thelike are read into the control device 24.

Next, in step S202, the target acceleration is set based on thedetection signals from the sensors read in step S201. The targetacceleration is set mainly based on the amount of depression of theaccelerator pedal (not illustrated) detected by the accelerator positionsensor 44 (FIG. 5). In contrast, when the driver depresses the brakepedal (not illustrated) with the intention of decelerating the vehicle1, the target acceleration is set to a negative value (the targetdeceleration is set). The target deceleration (negative targetacceleration) is set mainly based on the amount of depression of thebrake pedal detected by the brake sensor 46 (FIG. 5).

Next, in step S203, it is determined whether the speed of the vehicle 1detected by the vehicle speed sensor 42 is equal to or more than thepredetermined first vehicle speed. The processing proceeds to step S204when the speed is equal to or more than the predetermined first vehiclespeed or the processing proceeds to step S210 when the speed is lessthan the first vehicle speed. At time t₂₀₁ in FIG. 14, since the driverhas started the vehicle 1 and the vehicle speed is low, the processingof the flowchart proceeds to step S210. Although the predetermined firstvehicle speed is set to approximately 100 km/h in the embodiment, thepredetermined first vehicle speed may be set to a vehicle speed (forexample, approximately 50 km/h) less than this value depending on thecharacteristics of the main drive motor 16 and the auxiliary drivemotors 20 to be adopted.

Furthermore, in step S210, it is determined whether the targetacceleration of the vehicle 1 is a negative value (target decelerationor not). The processing proceeds to step S211 when the targetacceleration is less than zero or the processing proceeds to step S212when the target acceleration is positive or zero. Since the driver hasstarted and is accelerating the vehicle 1 (positive target accelerationis set) at time t₂₀₁ in FIG. 14, the processing of the flowchartproceeds to step S212. In step S212, it is determined whether the targetacceleration is a positive value (target acceleration or not). Theprocessing proceeds to step S213 when the target acceleration ispositive or the processing proceeds to step S214 when the targetacceleration is zero.

Since the positive target acceleration is set at time t₂₀₁, theprocessing proceeds to step S213 and, in step S213, the controlparameter for the main drive motor 16 is set so that the targetacceleration can be obtained by the driving force of the main drivemotor 16. In contrast, in step S213, the control parameter for theauxiliary drive motors 20 is set as to stop the motors (no driving forceis generated and no kinetic energy is regenerated). Next, the processingproceeds to step S206, the control parameter set in step S213 is sentfrom the control device 24 to the main drive motor 16 and the auxiliarydrive motors 20, and the processing of the flowchart in FIG. 13 iscompleted once. By receiving the control parameter in step S206, themain drive motor 16 generates a torque, increases the vehicle speed, andachieves the target acceleration (from time t₂₀₁ to time t₂₀₂ in FIG.14).

In the example illustrated in FIG. 14, the vehicle 1 is accelerated fromtime t₂₀₁ to time t₂₀₂. In this period, the processing of steps S201,S202, S203, S210, S212, S213, and S206 in the flowchart in FIG. 13 isrepeatedly executed.

Next, when the driver releases the accelerator pedal at time t₂₀₂ inFIG. 14, the target acceleration to be set in step S202 in FIG. 13becomes zero (constant speed travel). This causes the processing of theflowchart in FIG. 13 to proceed to step S214 from step S212. In stepS214, the control parameter for the main drive motor 16 is set so that aconstant speed travel is maintained by the driving force of the maindrive motor 16. That is, the control parameter is set so that the maindrive motor 16 generates a driving force corresponding to the travelresistance of the vehicle 1 and maintains a constant speed. Accordingly,the driving force generated by the main drive motor 16 becomes smallerthan the driving force during acceleration of the vehicle 1. Incontrast, in step S214, the control parameter for the auxiliary drivemotors 20 is set so as to stop the motors. Next, the processing proceedsto step S206, the control parameters set in step S214 are sent to theindividual motors, and the processing of the flowchart in FIG. 13 iscompleted once.

In the example illustrated in FIG. 14, the vehicle 1 travels at aconstant speed from time t₂₀₂ to time t₂₀₃. In this period, theprocessing of steps S201, S202, S203, S210, S212, S214, and S206 in theflowchart in FIG. 13 is repeatedly executed.

Next, when the driver depresses the accelerator pedal again at time t₂₀₃in FIG. 14, the target acceleration to be set in step S202 in FIG. 13becomes a positive value. This causes the processing of the flowchart inFIG. 13 to proceed to step S213 from step S212. As described above, instep S213, the control parameter for the main drive motor 16 is set sothat the set target acceleration is achieved and the control parameterfor the auxiliary drive motors 20 is set so as to stop the motors. Next,the processing proceeds to step S206, the control parameters set in stepS213 are sent to the individual motors and the processing of theflowchart in FIG. 13 is completed once.

In the example illustrated in FIG. 14, the vehicle 1 travels at aconstant acceleration from time t₂₀₃ to time t₂₀₄ and the speed thereofincreases. In this period, the processing of steps S201, S202, S203,S210, S212, S213, and S206 in the flowchart in FIG. 13 is repeatedlyexecuted.

Next, when the speed of the vehicle 1 reaches the predetermined firstvehicle speed (100 km/h in the embodiment) at time t₂₀₄, the processingof the flowchart in FIG. 13 proceeds to step S204 from step S203.

In step S204, it is determined whether the target acceleration of thevehicle 1 is a negative value (target deceleration or not). Theprocessing proceeds to step S205 when the target acceleration is lessthan zero or the processing proceeds to step S207 when the targetacceleration is positive or zero. Since the driver is accelerating thevehicle 1 (positive target acceleration is set) at time t₂₀₄ in FIG. 14,the processing of the flowchart proceeds to step S207. In step S207, itis determined whether the target acceleration is a positive value(target acceleration or not). The processing proceeds to step S208 whenthe target acceleration is positive or the processing proceeds to stepS209 when the target acceleration is zero.

Since the positive target acceleration is set at time t₂₀₄, theprocessing proceeds to step S208 and, in step S208, the controlparameters for the main drive motor 16 and the auxiliary drive motors 20are set so that the target acceleration can be obtained by the drivingforces of the main drive motor 16 and the auxiliary drive motors 20.When the vehicle 1 is accelerated in the state in which the speed of thevehicle 1 is equal to or more than the first vehicle speed, not only themain drive motor 16 but also the auxiliary drive motors 20 generatedriving forces. That is, the target acceleration set in step S202 isachieved by the driving forces generated by the main drive motor 16 andthe auxiliary drive motors 20. As described above, the auxiliary drivemotors 20 are used to assist the driving force of the main drive motor16 when the vehicle 1 is accelerated in the state in which the speed ofthe vehicle 1 is equal to or more than the first vehicle speed.

Next, the processing proceeds to step S206, the control parameters setin step S208 are sent to the main drive motor 16 and the auxiliary drivemotors 20, and the processing of the flowchart in FIG. 13 is completedonce. By receiving the control parameters in step S206, the main drivemotor 16 and the auxiliary drive motors 20 generate torques, increasethe vehicle speed, and achieve the target acceleration (from time t₂₀₄to time t₂₀₅ in FIG. 14). Although the individual motors output constanttorques with respect to a constant target acceleration in FIG. 14, thegraph of the motor torques is illustrated schematically. That is,although the travel resistance, the air resistance, and the like thatact on the vehicle 1 change due to a factor such as the vehicle speed,the torque actually required to maintain a constant target accelerationis not a constant value.

In the example illustrated in FIG. 14, the vehicle 1 travels at aconstant acceleration from time t₂₀₄ to time t₂₀₅ and the speed thereofincreases. In this period, the processing of steps S201, S202, S203,S204, S207, S208, and S206 in the flowchart in FIG. 13 is repeatedlyexecuted.

Next, when the driver releases the accelerator pedal at time t₂₀₅ inFIG. 14, the target acceleration to be set in step S202 in FIG. 13becomes zero (constant speed travel). This causes the processing of theflowchart in FIG. 13 to proceed to step S209 from step S207 and theprocessing of steps S201, S202, S203, S204, S207, S209, and S206 isrepeatedly executed. In step S209, the control parameters for the maindrive motor 16 and the auxiliary drive motors 20 are set so that aconstant speed travel is maintained by the driving forces of the maindrive motor 16 and the auxiliary drive motors 20. Next, the processingproceeds to step S206, the control parameters set in step S209 are sentto the individual motors and the processing of the flowchart in FIG. 13is completed once. It should be noted here that the present inventionmay be configured so that a constant speed travel is maintained only bythe driving forces of the auxiliary drive motors 20.

Next, when the driver operates the brake pedal (not illustrated) of thevehicle 1 at time t₂₀₆ in FIG. 14, the target acceleration to be set instep S202 of the flowchart in FIG. 13 becomes a negative value (targetdeceleration). This causes the processing of the flowchart to proceed tostep S205 from step S204 and the processing of steps S201, S202, S203,S205, and S206 is repeatedly executed. In step S205, the controlparameters for the main drive motor 16 and the auxiliary drive motors 20are set so that these motors regenerate the kinetic energy of thevehicle 1. Furthermore, when the set control parameters are sent to themain drive motor 16 and the auxiliary drive motors 20 in step S206, thekinetic energy is regenerated by these motors.

When the vehicle speed is reduced by an operation of the brake pedal(not illustrated) by the driver and the speed of the vehicle 1 becomesless than the predetermined first vehicle speed (100 km/h in theembodiment) at time t₂₀₇ in FIG. 14, the processing of the flowchartproceeds to step S210 and then step S211 from step S203 and theprocessing of steps S201, S202, S203, S210, S211, and S206 is repeatedlyexecuted. In step S211, the control parameters for the main drive motor16 and the auxiliary drive motors 20 are set so that the main drivemotor 16 stops (no driving force is generated and no kinetic energy isregenerated) and the auxiliary drive motors 20 regenerate the kineticenergy of the vehicle 1. In addition, when the set control parametersare sent to the main drive motor 16 and the auxiliary drive motors 20 instep S206, the kinetic energy is regenerated by the auxiliary drivemotors 20. This reduces the vehicle speed and the vehicle 1 stops attime t₂₀₈ in FIG. 14.

Next, a vehicle drive device that is a hybrid drive device according toa third embodiment of the present invention will be described withreference to FIG. 15 and FIG. 16.

The vehicle drive device according to the embodiment is different fromthe first embodiment in the control performed by the control device 24.Accordingly, since the structure of the vehicle drive device describedwith reference to FIG. 1 to FIG. 9 is the same as that of the firstembodiment, the description thereof will be omitted and only the pointsof the third embodiment of the present invention that are different fromthose of the first embodiment will be described.

FIG. 15 is a flowchart illustrating the control by the control deviceprovided in the vehicle drive device according to the third embodimentof the present invention and FIG. 16 is a graph illustrating one exampleof operation in the motor travel mode. The flowchart illustrated in FIG.15 indicates the processing (corresponding to the processing of step S2and subsequent steps in the flowchart illustrated in FIG. 10) that isexecuted when the mode selection switch 40 of the vehicle 1 is set tothe motor travel mode. The processing executed in the engine travel modeof the vehicle control device according to the embodiment is the same asthat of the first embodiment. In addition, the flowchart illustrated inFIG. 15 is repeatedly executed at predetermined time intervals while thevehicle 1 operates.

The graph illustrated in FIG. 16 represents, in order from the top, thespeed of the vehicle 1, the target acceleration of the vehicle 1 that isset based on a driving operation by the driver, the torque generated bythe engine 12, the torque generated by the main drive motor 16, and thetorque generated by the auxiliary drive motors 20. Since the graphillustrated in FIG. 16 represents the operation in the motor travelmode, the torque generated by the engine 12 is always set to zero. Inaddition, in the graph representing the torque of the main drive motor16 and the torque of the auxiliary drive motors 20, positive values meanthat motors are generating torques and negative values mean that motorsare regenerating the kinetic energy of the vehicle 1.

First, in step S301 in FIG. 15, detection signals from various sensorsare read. Specifically, detection signals from the vehicle speed sensor42, the accelerator position sensor 44, the brake sensor 46, and thelike are read into the control device 24.

Next, in step S302, the target acceleration is set based on thedetection signals from the sensors read in step S301. The targetacceleration is set mainly based on the amount of depression of theaccelerator pedal (not illustrated) detected by the accelerator positionsensor 44 (FIG. 5). In contrast, when the driver depresses the brakepedal (not illustrated) with the intention of decelerating the vehicle1, the target acceleration is set to a negative value (the targetdeceleration is set). The target deceleration (negative targetacceleration) is set mainly based on the amount of depression of thebrake pedal detected by the brake sensor 46 (FIG. 5).

Next, in step S303, it is determined whether the speed of the vehicle 1detected by the vehicle speed sensor 42 is equal to or more than thepredetermined first vehicle speed. The processing proceeds to step S304when the speed is equal to or more than the predetermined first vehiclespeed or the processing proceeds to step S312 when the speed is lessthan the first vehicle speed. At time t₃₀₁ in FIG. 16, since the driverhas started the vehicle 1 and the vehicle speed is low, the processingof the flowchart proceeds to step S312. The predetermined first vehiclespeed is also set to approximately 100 km/h in the embodiment.

Furthermore, in step S312, it is determined whether the targetacceleration of the vehicle 1 is a negative value (target decelerationor not). The processing proceeds to step S313 when the targetacceleration is less than zero or the processing proceeds to step S314when the target acceleration is positive or zero. Since the driver hasstarted and is accelerating the vehicle 1 (positive target accelerationis set) at time t₃₀₁ in FIG. 16, the processing of the flowchartproceeds to step S314. In step S314, it is determined whether the targetacceleration is a positive value (target acceleration or not). Theprocessing proceeds to step S315 when the target acceleration ispositive or the processing proceeds to step S311 when the targetacceleration is zero.

Since the positive target acceleration is set at time t₃₀₁, theprocessing proceeds to step S315 and, in step S315, the controlparameters for the main drive motor 16 are set so that the targetacceleration can be obtained by the driving force of the main drivemotor 16. In contrast, in step S315, the control parameter for theauxiliary drive motors 20 is set so as to stop the motors (no drivingforce is generated and no kinetic energy is regenerated). Next, theprocessing proceeds to step S306, the control parameters set in stepS315 are sent from the control device 24 to the main drive motor 16 andthe auxiliary drive motors 20, and the processing of the flowchart inFIG. 13 is completed once. By receiving the control parameters in stepS306, the main drive motor 16 generates a torque, increases the vehiclespeed, and achieves the target acceleration (from time t₃₀₁ to time t₃₀₂in FIG. 14).

In the example illustrated in FIG. 16, the vehicle 1 is accelerated fromtime t₃₀₁ to time t₃₀₂. In this period, the processing of steps S301,S302, S303, S312, S314, S315, and S306 in the flowchart in FIG. 15 isrepeatedly executed.

Next, when the driver releases the accelerator pedal at time t₃₀₂ inFIG. 16, the target acceleration to be set in step S302 in FIG. 15becomes zero (constant speed travel). This causes the processing of theflowchart in FIG. 15 to proceed to step S311 from step S314. In stepS311, the control parameter for the main drive motor 16 is set so that aconstant speed travel is maintained by the driving force of the maindrive motor 16. That is, the control parameter is set so that the maindrive motor 16 generates a driving force corresponding to the travelresistance of the vehicle 1 and maintains a constant speed. Accordingly,the driving force generated by the main drive motor 16 becomes smallerthan the driving force during acceleration of the vehicle 1. Incontrast, in step S311, the control parameter for the auxiliary drivemotors 20 is set so as to stop the motors. Next, the processing proceedsto step S306, the control parameters set in step S311 are sent to theindividual motors, and the processing of the flowchart in FIG. 15 iscompleted once.

In the example illustrated in FIG. 16, the vehicle 1 travels at aconstant speed from time t₃₀₂ to time t₃₀₃. In this period, theprocessing of steps S301, S302, S303, S312, S314, S311, and S306 in theflowchart in FIG. 15 is repeatedly executed.

Next, when the driver depresses the accelerator pedal again at time t₃₀₃in FIG. 16, the target acceleration to be set in step S302 in FIG. 15becomes a positive value. This causes the processing of the flowchart inFIG. 15 to proceed to step S315 from step S314. As described above, instep S315, the control parameter for the main drive motor 16 is set soas to achieve the set target acceleration and the control parameter forthe auxiliary drive motors 20 is set so as to stop the motors. Next, theprocessing proceeds to step S306, the control parameters set in stepS315 are sent to the individual motors, and the processing of theflowchart in FIG. 15 is completed once.

In the example illustrated in FIG. 16, the vehicle 1 travels at aconstant acceleration from time t₃₀₃ to time t₃₀₄ and the speed thereofincreases. In this period, the processing of steps S301, S302, S303,S312, S314, S315, and S306 in the flowchart in FIG. 15 is repeatedlyexecuted.

Next, when the speed of the vehicle 1 reaches the predetermined firstvehicle speed (100 km/h in the embodiment) at time t₃₀₄, the processingof the flowchart in FIG. 15 proceeds to step S304 from step S303.

In step S304, it is determined whether the target acceleration of thevehicle 1 is a negative value (target deceleration or not). Theprocessing proceeds to step S305 when the target acceleration is lessthan zero or the processing proceeds to step S307 when the targetacceleration is positive or zero. Since the driver is acceleratingvehicle 1 (positive target acceleration is set) at time t₃₀₄ in FIG. 16,the processing of the flowchart proceeds to step S307. In step S307, itis determined whether the target acceleration is a positive value(target acceleration or not). The processing proceeds to step S308 whenthe target acceleration is positive or the processing proceeds to stepS311 when the target acceleration is zero.

Since the positive target acceleration is set at time t₃₀₄, theprocessing proceeds to step S308 and, in step S308, it is determinedwhether the target acceleration is equal to or more than thepredetermined first acceleration. Since the acceleration at time t₃₀₄ isless than the predetermined first acceleration in the exampleillustrated in FIG. 16, the processing proceeds to step S309. Althoughthe predetermined first acceleration is set to approximately 1.5 m/sec²in the embodiment, a different first acceleration may be set dependingon the characteristics of the main drive motor 16 and the auxiliarydrive motors 20 to be adopted. For example, the predetermined firstacceleration can be set within the range from approximately 1.5 to 2.5m/sec². In step S309, the control parameter for the main drive motor 16is set so as to achieve the set target acceleration and the controlparameter for the auxiliary drive motors 20 is set so as to stop themotors.

Next, the processing proceeds to step S306, the control parameters setin step S309 are sent to the main drive motor 16 and the auxiliary drivemotors 20, and the processing of the flowchart in FIG. 15 is completedonce. By receiving the control parameter in step S306, the main drivemotor 16 generates a torque and achieves the target acceleration (fromtime t₃₀₄ to time t₃₀₅ in FIG. 16). In the example illustrated in FIG.16, the vehicle 1 travels at a constant acceleration from time t₃₀₄ totime t₃₀₅ and the speed thereof increases. In this period, theprocessing of steps S301, S302, S303, S304, S307, S308, S309, and S306in the flowchart in FIG. 15 is repeatedly executed.

Next, when the driver further depresses the accelerator pedal at timet₃₀₅ and the target acceleration to be set in step S302 becomes equal toor more than the predetermined first acceleration, the processing of theflowchart in FIG. 15 proceeds to step S310 from step S308. In step S310,the control parameters for the main drive motor 16 and the auxiliarydrive motors 20 are set so that the target acceleration can be obtainedby the driving forces of the main drive motor 16 and the auxiliary drivemotors 20. As described above, in the embodiment, when accelerationequal to or more than the first acceleration is performed in the statein which the speed of the vehicle 1 is the first vehicle speed or more,the auxiliary drive motors 20 also generate driving forces in additionto the main drive motor 16. That is, the target acceleration set in stepS302 is achieved by the driving forces generated by the main drive motor16 and the auxiliary drive motors 20. As described above, the auxiliarydrive motors 20 are used to assist the driving force of the main drivemotor 16 when the vehicle 1 is accelerated with the first accelerationor more in the state in which the speed of the vehicle 1 is the firstvehicle speed or more.

Next, the processing proceeds to step S306, the control parameters setin step S310 are sent to the main drive motor 16 and the auxiliary drivemotors 20, and the processing of the flowchart in FIG. 15 is completedonce. By receiving the control parameter in step S306, the main drivemotor 16 and the auxiliary drive motors 20 generate torques, increasethe vehicle speed, and achieve the target acceleration (from time t₃₀₅to time t₃₀₆ in FIG. 16). In the example illustrated in FIG. 16, thevehicle 1 travels at a constant acceleration from time t₃₀₅ to time t₃₀₆and the speed thereof increases. In this period, the processing of stepsS301, S302, S303, S304, S307, S308, S310, and S306 in the flowchart inFIG. 15 is repeatedly executed.

Next, when the driver releases the accelerator pedal at time t₃₀₆ inFIG. 16, the target acceleration to be set in step S302 in FIG. 15becomes zero (constant speed travel). This causes the processing of theflowchart in FIG. 15 to proceed to step S311 from step S307 and theprocessing of steps S301, S302, S303, S304, S307, S311, and S306 isrepeatedly executed. In step S311, the control parameters for the maindrive motor 16 and the auxiliary drive motors 20 are set so that aconstant speed travel is maintained by the driving force of the maindrive motor 16 (the auxiliary drive motors 20 stop). Next, theprocessing proceeds to step S306, the control parameters set in stepS311 are sent to the individual motors, and the processing of theflowchart in FIG. 15 is completed once. It should be noted here that thepresent invention may be configured so that a constant speed travel ismaintained only by the driving forces of the auxiliary drive motors 20.

Next, when the driver operates the brake pedal (not illustrated) of thevehicle 1 at time t₃₀₇ in FIG. 16, the target acceleration to be set instep S302 of the flowchart in FIG. 15 becomes a negative value (targetdeceleration). This causes the processing of the flowchart to proceed tostep S305 from step S304 and the processing of steps S301, S302, S303,S304, S305, and S306 is repeatedly executed. In step S305, the controlparameters for the main drive motor 16 and the auxiliary drive motors 20are set so that these motors regenerate the kinetic energy of thevehicle 1. Furthermore, when the set control parameters are sent to themain drive motor 16 and the auxiliary drive motors 20 in step S306, thekinetic energy is regenerated by these motors.

The speed of the vehicle 1 is reduced by an operation of the brake pedal(not illustrated) by the driver to less than the predetermined firstvehicle speed (100 km/h in the embodiment) at time t₃₀₈ in FIG. 16, theprocessing of the flowchart proceeds to step S312 and then S313 fromstep S303 and the processing of steps S301, S302, S303, S312, S313, andS306 is repeatedly executed. In step S313, the control parameters forthe main drive motor 16 and the auxiliary drive motors 20 are set sothat the main drive motor 16 stops (no driving force is generated and nokinetic energy is regenerated) and the auxiliary drive motors 20regenerate the kinetic energy of the vehicle 1. Furthermore, when theset control parameters are sent to the main drive motor 16 and theauxiliary drive motors 20 in step S306, the auxiliary drive motors 20regenerate the kinetic energy. This reduces the vehicle speed and thevehicle 1 stops at time t₃₀₉ in FIG. 16.

The vehicle drive devices according to the first to third embodiments ofthe present invention have been described above. Although the vehicledrive device according to the present invention is applied to an FRvehicle in any of the first to third embodiments described above, thepresent invention is applicable to various types of vehicles such as aso-called FF vehicle in which an engine and/or a main drive motor aredisposed in the front portion of the vehicle and the front wheels arethe main drive wheels or a so-called RR vehicle in which an engineand/or a main drive motor are disposed in the rear portion of thevehicle and the rear wheels are the main drive wheels.

When the present invention is applied to an FF vehicle, it is possibleto adopt a layout in which, for example, the engine 12, the main drivemotor 16, and the transmission 14c are disposed in the front portion ofa vehicle 101 and front wheels 102 a are driven as the main drivewheels, as illustrated in FIG. 17. In addition, the auxiliary drivemotors 20 can be disposed as in-wheel motors in the left and right rearwheels 102 b, which are the auxiliary drive wheels. As described above,the present invention can be configured so that the main drive motor 16,which is the body side motor, drives the front wheels 102 a, which arethe main drive wheels, and the auxiliary drive motors 20, which are thein-wheel motors, drive the rear wheels 102 b, which are the auxiliarydrive wheels. In this layout, the main drive motor 16 can be driven bythe electric power supplied via the inverter 16 a and stored in thebattery 18. In addition, an integrated unit formed by integrating thecapacitor 22, the high voltage DC/DC converter 26 a and the low voltageDC/DC converter 26 b, which are voltage converting units, and the twoinverters 20 a can be disposed in the rear portion of the vehicle 101.Furthermore, the auxiliary drive motors 20 can be driven by the electricpower supplied via the inverters 20 a and stored in the battery 18 andthe capacitor 22 that are disposed in series.

When the present invention is applied to an FF vehicle, it is possibleto adopt a layout in which, for example, the engine 12, the main drivemotor 16, and the transmission 14c are disposed in the front portion ofa vehicle 201, and the front wheels 202 a are driven as the main drivewheels, as illustrated in FIG. 18. In addition, the auxiliary drivemotors 20 can be disposed as in-wheel motors in the left and right frontwheels 202 a, which are the main drive wheels. As described above, thepresent invention can be configured so that the main drive motor 16,which is the body side motor, drives the front wheels 202 a, which arethe main drive wheels, and the auxiliary drive motors 20, which are thein-wheel motors, also drive the front wheels 202 a, which are the maindrive wheels. In this layout, the main drive motor 16 can be driven bythe electric power supplied via the inverter 16 a and stored in thebattery 18. In addition, an integrated unit formed by integrating thecapacitor 22, the high voltage DC/DC converter 26 a and the low voltageDC/DC converter 26 b, which are voltage converting units, and the twoinverters 20 a can be disposed in the rear portion of the vehicle 201.Furthermore, the auxiliary drive motors 20 can be driven by the electricpower supplied via the inverters 20 a and stored in the battery 18 andthe capacitor 22 that are disposed in series.

In contrast, when the present invention is applied to an FR vehicle, itis possible to adopt a layout in which, for example, the engine 12 andthe main drive motor 16 are disposed in the front portion of a vehicle301 and rear wheels 302 b are driven as the main drive wheels by leadingelectric power to the rear portion of the vehicle 301 via the propellershaft 14a, as illustrated in FIG. 19. The rear wheels 302 b are drivenby the power led to the rear portion by the propeller shaft 14 a via theclutch 14 b and the transmission 14 c, which is a stepped transmission.In addition, the auxiliary drive motors 20 can be disposed as in-wheelmotors in the left and right rear wheels 302 b, which are the main drivewheels. As described above, the present invention can be configured sothat the main drive motor 16, which is the body side motor, drives therear wheels 302 b, which are the main drive wheels, and the auxiliarydrive motors 20, which are the in-wheel motors, also drive the rearwheels 302 b, which are the main drive wheels. In this layout, the maindrive motor 16 can be driven by the electric power supplied via theinverter 16 a and stored in the battery 18. In addition, an integratedunit formed by integrating the capacitor 22, the high voltage DC/DCconverter 26 a and the low voltage DC/DC converter 26 b, which arevoltage converting units, and the two inverters 20 a can be disposed inthe front portion of the vehicle 301. Furthermore, the auxiliary drivemotors 20 can be driven by the electric power supplied via the inverters20 a and stored in the battery 18 and the capacitor 22 that are disposedin series.

Although preferred embodiments of the present invention have beendescribed above, various modifications can be made to the embodimentsdescribed above. In particular, the present invention is applied to ahybrid drive device including an engine and a motor in the embodimentsdescribed above, but the present invention is applicable to a vehicledrive device that drives a vehicle only by a motor without having anengine.

REFERENCE CHARACTERS LIST

1: vehicle

2 a: rear wheel (main drive wheel)

2 b: front wheel (auxiliary drive wheel)

4 a: subframe

4 b: front side frame

4 c: dash panel

4 d: propeller shaft tunnel

6 a: engine mount

6 b: capacitor mount

8 a: upper arm

8 b: lower arm

8 c: spring

8 d: shock absorber

10: hybrid drive device (vehicle drive device)

12: engine (internal combustion engine)

14: power transmission mechanism

14 a: propeller shaft

14 b: clutch

14 c: transmission (stepped transmission, automatic transmission)

14 d: torque tube

16: main drive motor (main drive electric motor, body side motor)

16 a: inverter

18: battery (electric storage unit)

20: auxiliary drive motor (auxiliary drive electric motor, in-wheelmotor)

20 a inverter

22: capacitor

22 a: bracket

22 b: harness

24: control device (controller)

25: electrical component

26 a: high voltage DC/DC converter (voltage converting unit)

26 b: low voltage DC/DC converter

28: stator

28 a: stator base

28 b: stator shaft

28 c: stator coil

30: rotor

30 a: rotor body

30 b: rotor coil

32: electrical insulating liquid chamber

32 a: electrical insulating liquid

34: bearing

40: mode selection switch

42: vehicle speed sensor

44: accelerator position sensor

46: brake sensor

48: engine RPM sensor

50: automatic transmission input rotation sensor

52: automatic transmission output rotation sensor

54: voltage sensor

56: current sensor

58: fuel injection valve

60: spark plug

62: hydraulic solenoid valve

101: vehicle

102 a: front wheel (main drive wheel)

102 b: rear wheel (auxiliary drive wheel)

201: vehicle

202 a: front wheel (main drive wheel)

301: vehicle

302 b: rear wheel (main drive wheel)

1. A vehicle drive device that uses an in-wheel motor to drive avehicle, the vehicle drive device comprising: a vehicle speed sensorthat detects a travel speed of the vehicle; an in-wheel motor that isprovided in a wheel of the vehicle and drives the wheel; and acontroller that controls the in-wheel motor, wherein the controllercontrols the in-wheel motor so as to generate a driving force when thetravel speed of the vehicle detected by the vehicle speed sensor isequal to or more than a predetermined first vehicle speed that is morethan zero.
 2. The vehicle drive device according to claim 1, furthercomprising: a body side motor that is provided in a body of the vehicleand drives the wheel of the vehicle, wherein the controller controls thebody side motor so as to generate a driving force when the travel speedof the vehicle detected by the vehicle speed sensor is less than apredetermined second vehicle speed.
 3. The vehicle drive deviceaccording to claim 2, wherein the controller also controls the body sidemotor so as to generate the driving force when the travel speed of thevehicle detected by the vehicle speed sensor is equal to or more thanthe second vehicle speed.
 4. The vehicle drive device according to claim1, wherein the controller controls the in-wheel motor so as not togenerate the driving force when the travel speed of the vehicle detectedby the vehicle speed sensor is less than the first vehicle speed.
 5. Thevehicle drive device according to claim 1, wherein the controller startsthe vehicle by causing the body side motor to generate the driving forceand then causes the in-wheel motor to generate the driving force whenthe travel speed of the vehicle detected by the vehicle speed sensorreaches the first vehicle speed.
 6. The vehicle drive device accordingto claim 1, wherein the in-wheel motor directly drives the wheel inwhich the in-wheel motor is provided, without intervention of adeceleration mechanism.
 7. The vehicle drive device according to claim1, wherein the in-wheel motor is an induction motor.
 8. The vehicledrive device according to claim 2, wherein the body side motor is apermanent magnet motor.
 9. The vehicle drive device according to claim2, wherein the wheel driven by the in-wheel motor is a front wheel ofthe vehicle and the wheel driven by the body side motor is a rear wheelof the vehicle.
 10. The vehicle drive device according to claim 2,wherein the wheel driven by the in-wheel motor is a rear wheel of thevehicle and the wheel driven by the body side motor is a front wheel ofthe vehicle.
 11. The vehicle drive device according to claim 2, whereinthe wheel driven by the in-wheel motor and the body side motor is afront wheel of the vehicle.
 12. The vehicle drive device according toclaim 2, wherein the wheel driven by the in-wheel motor and the bodyside motor is a rear wheel of the vehicle.
 13. A vehicle drive devicethat uses an in-wheel motor to drive a vehicle, the vehicle drive devicecomprising: a vehicle speed sensor that detects a travel speed of thevehicle; an in-wheel motor that is provided in a wheel of the vehicleand drives the wheel; and a controller that controls the in-wheel motor,wherein the controller controls the in-wheel motor so as not to generatethe driving force when the travel speed of the vehicle detected by thevehicle speed sensor is less than a predetermined first vehicle speedthat is more than zero.
 14. A vehicle drive device that uses an in-wheelmotor to drive a vehicle, the vehicle drive device comprising: a vehiclespeed sensor that detects a travel speed of the vehicle; an in-wheelmotor that is provided in a wheel of the vehicle and drives the wheel; abody side motor that is provided in a body of the vehicle and drives thewheel of the vehicle; and a controller that controls the in-wheel motorand the body side motor, wherein the controller starts the vehicle bycausing the body side motor to generate the driving force and thencauses the in-wheel motor to generate the driving force when the travelspeed of the vehicle detected by the vehicle speed sensor reaches afirst predetermined vehicle speed that is more than zero.